This invention relates to surface-mountable antennas usable in mobile communication apparatus and a method of adjusting the resonant frequency of such an antenna.
As an example of prior art antennas adapted for surface mounting, K. Fujimoto, A. Henderson, K. Hirasawa and J. R. James disclosed (in "Small Antennas" published by Research Studies Press, Ltd., England) an inverted-F antenna 71 which, as shown in FIG. 5, has a rectangular metallic plate 72 serving as a radiation emitter, a grounding terminal 73 formed by bending perpendicularly from one side edge of the metallic plate 72, and a power feed terminal 74 formed similarly by bending perpendicularly from another side edge of the metallic plate 72. An inverted-F antenna, thus structured, can be mounted to a circuit board of a known kind by inserting its grounding and power feed terminals into throughholes, many of which are usually provided to the circuit board.
Such a prior art antenna, however, could not be surface-mounted to a printed circuit board, unless throughholes are specifically provided for having the grounding and power feed terminals inserted thereinto. Moreover, adjustments of resonant frequency of such a prior art antenna were difficult because it had to be done by trimming the metallic plate 72 which is a main component of the antenna.